Description: Plan 21 is recirculation from pump discharge
through an 1/8” minimum flow control orifice (when
necessary), and seal flush cooler, then into the seal chamber.
Objective: Cool the process in the seal chamber, improving
lubricity and increasing the vapor margin. Reduce coking.
Advantages: Provides cooling through a seal flush cooler.
When used with a close‐clearance throat bushing, it can raise
the pressure in the seal
Plan 23 when used in
viscous applications that
may clog seal flush
Note: Plan 23 is the preferred plan due to
high heat loads put on the seal flush
cooler when using Plan 21.